Dominant mutations in p63, a transcription factor expressed as six isoforms, underlie the skin fragility syndrome ankyloblepharon ectodermal dysplasia and defting (AEG). Skin erosions that resemble those found in AEG patients develop in mice with reduced Delta-Np63 expression. The proposed studies will dissect the regulatory pathways by which Delta-Np63 controls normal epidermal homeostasis and will provide insight into the disease mechanism underlying AEG. We have recently identified Fras1 and Galml4 as direct transcriptional targets of Delta-Np63. Misexpression of these genes may contribute to the AEG phenotype. To further study the role of these genes in embryonic and postnatal skin, we will develop mouse models in which the expression of these genes is altered. These mouse models will allow us to determine the role of Frasi in regulating basement membrane integrity in postnatal epidermis. Furthermore, we will use these mouse models to determine the role of Calml4 in epidermal terminal differentiation. Our analysis of Calml4 function in keratinocyte terminal differentiation will be completed by performing proteomics and microarray analysis. Ultimately, the proposed studies will contribute to our understanding of the molecular mechanisms that cause skin fragility in AEG patients, and may identify targets for novel therapeutic approaches aimed at treating this disease.